scholarly journals Picosecond Flash Photolysis of Photochromic Spiropyrans

1984 ◽  
Vol 4 (1-6) ◽  
pp. 129-138 ◽  
Author(s):  
S. A. Krysanov ◽  
M. V. Alfimov
Keyword(s):  
Room Temperature ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Decay Channel ◽  
Transient Absorption Spectrum ◽  
Colored Form ◽  
Pyran Ring ◽  
Decay Times ◽  
Buildup Time

The transient species involved in photocoloration and photobleaching of indoline 6-nitrosubstituted spiropyran solutions at room temperature were studied by picosecond flash photolysis. Transient absorption spectrum of spiropyran colorless form consists of two bands peaked at 440 and 585 nm and is assigned to the photoinduced intermediate non-planar cis configuration with the breaked C—O bond of the pyran ring. This transient is found to have the buildup time shorter than 10 ps and initial decay times of about 10 ns in benzene and 5 ns in ethanol. The colored form exhibits the transient absorption peaked at 460 nm with the lifetime of about 200 ps in ethanol which is assigned to Sn ← S1 absorption of colored form. The predominant decay channel of the colored form S1 state is shown to be internal conversion S1 ⇝ S0 with the quantum yield of about 0.70 ± 0.15.

Clocking the buildup dynamics of light-induced states through attosecond transient absorption spectrum

2021 ◽  
Author(s):  
Xiaoxia Wu ◽  
Shaofeng Zhang ◽  
Difa Ye
Keyword(s):  
Floquet Theory ◽  
Transient Absorption ◽  
Scaling Law ◽  
Time Lag ◽  
Time Dependent ◽  
Transient Absorption Spectroscopy ◽  
Transient Absorption Spectrum ◽  
Wide Range ◽  
Maximal Shift ◽  
Buildup Time

Abstract The buildup processes of the light-induced states (LISs) in attosecond transient absorption spectroscopy are studied by solving the time-dependent Schrödinger equation and compared with the quasistatic Floquet theory, revealing a time lag of the maximal shift and strongest absorbance of the LIS with respect to the zero delay that is referred to as the buildup time. We analytically derive a scaling law for the buildup time that confirms the numerical results over a wide range of detunings. Our theory verifies the commonly accepted scenario of nearly instantaneous response of matter to light if the pump field is blue-detuned, but some differences are found in the near-resonant and red-detuning cases. Implications of the buildup time in petahertz optoelectronics are discussed.

Photochemical Properties of 2-Aryl-3-imino-1-indones

1992 ◽  
Vol 47 (12) ◽  
pp. 1243-1247 ◽  
Author(s):  
I. Timtcheva ◽  
N. Getoff ◽  
P. Nikolov ◽  
R. M. Quint
Keyword(s):  
Absorption Spectrum ◽  
Steady State ◽  
Reaction Mechanisms ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Uv Light ◽  
Transient Absorption Spectrum ◽  
Light Illumination ◽  
Probable Reaction ◽  
Photochemical Properties

Steady state as well as flash photolysis experiments of 2-aryl-3-imino-1-indones (2-AIID) have been carried out with the aim to learn more about their photochemical properties. It was established that in ethanol these substances exist solely in the keto-enamine-form and are rather photostable under the influence of uv-light. Illumination in dichloroethane, acetonitrile and dioxane is leading to stable photoproducts. A typical transient absorption spectrum of 2-AIID is presented. Probable reaction mechanisms are given.

Photoinduced electron transfer in a supramolecular triad system composed of ferrocene-zinc porphyrin-pyridylnaphtha-lenediimide

2007 ◽  
Vol 11 (05) ◽  
pp. 368-374 ◽  
Author(s):  
Shunichi Fukuzumi ◽  
Yukiyasu Kashiwagi
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Zinc Ion ◽  
Transient Absorption Spectrum ◽  
Zinc Porphyrin ◽  
Long Lifetime ◽  
Porphyrin Moiety

A supramolecular ferrocene-zinc porphyrin-pyridylnaphthalenediimide triad is formed by coordinating the pyridine entity of pyridylnaphthalenediimide with the zinc ion of a ferrocene-zinc porphyrin dyad in benzonitrile. The fluorescence of the zinc porphyrin moiety is efficiently quenched by photoinduced electron transfer from the singlet excited state of the zinc porphyrin moiety to the naphthalenediimide moiety. This is followed by subsequent electron transfer from the ferrocene moiety to the zinc porphyrin radical cation to produce the final charge-separated state, ferricenium ion-zinc porphyrin-naphthalenediimide radical anion, which is successfully detected as a transient absorption spectrum in the laser flash photolysis. The decay of the charge-separated state obeys first-order kinetics irrespective of the initial concentration of the charge-separated state to afford a long lifetime (320 μs). This is the first example of a supramolecular triad that has a long lifetime as compared with the charge-separated state lifetime of the component dyad.

ROTATIONAL ANALYSIS OF BANDS OF THE HCF MOLECULE

1966 ◽  
Vol 44 (7) ◽  
pp. 1541-1550 ◽  
Author(s):  
A. J. Merer ◽  
D. N. Travis
Keyword(s):  
Transient Absorption ◽  
Flash Photolysis ◽  
Bond Angle ◽  
Large Change ◽  
Transient Absorption Spectrum ◽  
Rotational Analysis ◽  
Molecular Constants ◽  
Ordinary Type ◽  
Type C ◽  
Axis Switching

A new transient absorption spectrum, belonging to the HCF free radical, has been discovered in the flash photolysis of dibromofluoromethane, HCFBr2. The spectrum consists of a single progression of complex bands in the region 4 300–6 000 Å. Rotational analysis of the less severely perturbed bands shows them to be type-C bands of a molecule that is nonlinear in both upper and lower states of the transition, with bond angles of ~ 127° and ~ 102° respectively. Axis-switching effects, due to the large change of bond angle in the transition, cause the appearance of prominent gQ, qQ, and °Q branches, in addition to those obeying the ordinary type-C selection rules.The principal molecular constants of HCF (in cm−1) are:[Formula: see text]

An extremely long-lived charge-separated state of zinc tetraphenylporphyrin coordinated with pyridylnaphthalene-diimide

2006 ◽  
Vol 10 (12) ◽  
pp. 1371-1379 ◽  
Author(s):  
Kenji Saito ◽  
Yukiyasu Kashiwagi ◽  
Kei Ohkubo ◽  
Shunichi Fukuzumi
Keyword(s):  
Photoinduced Electron Transfer ◽  
Lower Energy ◽  
Transient Absorption ◽  
Laser Excitation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Transient Absorption Spectrum ◽  
Triplet Excited State ◽  
Donor Acceptor

The nitrogen of pyridylnaphthalenediimide ( PyNIm ) coordinates to the metal center of zinc tetraphenylporphyrin ( ZnTPP ) to form a donor-acceptor complex: ZnTPP-PyNIm . Formation of the ZnTPP-PyNIm complex was probed by UV-vis, fluorescence and NMR spectra. The fluorescence of ZnTPP is strongly quenched and the fluorescence lifetime is shortened significantly in the complex. The transient absorption spectrum of the charge-separated state ( ZnTPP •+- PyNIm •-) is successfully detected by laser flash photolysis measurements of the ZnTPP-PyNIm system in benzonitrile. The charge-separated state of the complex produced by the photoinduced electron transfer has the longest lifetime, (450 μs) at 288 K, ever reported for donor-acceptor systems linked covalently or non-covalently in solution. However, when benzonitrile is replaced by benzene, the triplet excited state (3 ZnTPP* ), rather than the charge-separated state, is formed upon laser excitation of the ZnTPP-PyNIm complex, due to the lower energy of (3 ZnTPP* ) compared to the charge-separated state in benzene.

ABSORPTION SPECTRUM OF THE CCN RADICAL

1965 ◽  
Vol 43 (10) ◽  
pp. 1795-1830 ◽  
Author(s):  
A. J. Merer ◽  
D.N. Travis
Keyword(s):  
Absorption Spectrum ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Energy Levels ◽  
Transient Absorption Spectrum ◽  
Molecular Constants ◽  
Angular Momenta ◽  
Show Evidence ◽  
Vibrational Energy Levels

A new transient absorption spectrum, attributed to the CCN free radical, has been discovered in the flash photolysis of diazoacetonitrile, HC(CN)N2; three electronic transitions, between 3 500 Å and 4 700 Å, have been photographed for both CC14N and CC15N. The ground state of the radical is a 2Πr electronic state, and the three excited states observed are A2Δ, B2Σ−, and C2Σ+. The 2Π and 2Δ states show evidence of Renner–Teller interaction between the vibrational and electronic angular momenta, an effect not observed previously for 2Δ states. Theoretical expressions for the vibrational energy levels of linear triatomic molecules in 2Δ electronic states have been derived, in terms of a parameter η associated with the quartic terms in the potential energy. They are compared with the observed pattern in the ν2 = 1 level of the A2Δ state. The principal molecular constants for CC14N (in cm−1) are as follows:[Formula: see text]

Multiple photosynthetic reaction centers composed of supramolecular assemblies of a zinc porphyrin dendrimer with pyridylnaphthalenediimide

2011 ◽  
Vol 15 (11n12) ◽  
pp. 1292-1298 ◽  
Author(s):  
Shunichi Fukuzumi ◽  
Kei Ohkubo ◽  
Kenji Saito ◽  
Yukiyasu Kashiwagi ◽  
Tony Khoury ◽  
...  
Keyword(s):  
Excited State ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Supramolecular Complex ◽  
Reaction Centers ◽  
Transient Absorption Spectrum ◽  
Singlet Excited State ◽  
Photosynthetic Reaction Centers ◽  
Zinc Porphyrin

Multiple photosynthetic reaction centers have successfully been constructed using a supramolecular complex of zinc porphyrin dendrimer [D(ZnP)16] with pyridylnaphthalenediimide (PyNIm) in benzonitrile. The apparent formation constant determined from the fluorescence quenching of the singlet excited state of porphyrin moieties by PyNIm is significantly larger than that determined from the UV-vis spectral change. This indicates that efficient energy migration occurs between the porphyrin units of the dendrimer prior to the electron transfer from the singlet excited state of zinc porphyrin to PyNIm. The charge-separated (CS) state has been successfully detected as the transient absorption spectrum in the laser flash photolysis. The CS lifetime of in the supramolecular complex of D(ZnP)16 with PyNIm was determined to be 0.83 ms at 298 K.

The Band System of the CCO Molecule

1971 ◽  
Vol 49 (22) ◽  
pp. 2839-2858 ◽  
Author(s):  
C. Devillers ◽  
D. A. Ramsay
Keyword(s):  
Transient Absorption ◽  
Flash Photolysis ◽  
Energy Levels ◽  
Fermi Resonance ◽  
Lower State ◽  
Linear Molecule ◽  
Transient Absorption Spectrum ◽  
Rotational Analysis ◽  
Molecular Constants ◽  
Sequence Band

The transient absorption spectrum observed previously (Devillers) in the flash photolysis of carbon suboxide has been studied under high resolution in the region 5000 to 9000 Å and assigned to the CCO radical. A rotational analysis of the 000–000 band near 8580 Å shows conclusively that the electronic transition is [Formula: see text]. From molecular orbital considerations the lower state is assigned as [Formula: see text]. Short progressions involving the stretching vibrations (ν1′ = 0–3, ν3′ = 0–1) have been observed. A Fermi resonance has been found involving ν3′ and 2ν2′. Some sequence bands have been assigned; in particular the 010–010 sequence band clearly shows the Renner splittings expected for the Ã3Πi excited state. A band with a different type of rotational structure has been assigned to the forbidden component 010 3Σ(−) – 000 3Σ−. The rotational analysis of this band is in excellent agreement with the theory of Hougen for the rotational energy levels of a linear molecule in the ν2 = 1 level of a 3Π state.The following molecular constants have been obtained:[Formula: see text]

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